Biology Midterm 1 typed set Flashcards
Where are most of the genes held in eukaryotic cells?
The nucleus
How is the nucleus composed in eukaryotic cells?
Double membrane nuclear envelope surrounds nucleus, enclosing genetic material (chromosomes) and separates nuclear contents from the cytoplasm
The nucleolus is where rRNA is transcribed. The rRNA binds to proteins to form ribosomal subunits. Then it is exported out to the cytoplasm.
The nuclear pore complexes allows materials to flow in and out of the cell.
The chromosomes are within the middle of the nucleus between the nuclear membrane and the nucleolus
Where are the structure components of rRNA synthesized?
In the nucleolus, then the subunits of ribosomes containing protein and RNA form, and ship out to the cytoplasm
What are the options of ribosomes after they have been shipped out?
They can remain soluble in the cytoplasm as free ribosomes
OR
Attach onto the ER and become bound ribosomes
Bound ribosomes
Ribosomes on the ER
Free ribosomes
Ribosomes that are freely within the cytoplasm
Draw out and describe the structure of an amino acid
Refer to notes
How many amino acids in total are there
20
What is the only difference between the amino acid monomers which determines the properties of the entire amino acid
The R-group
Amino acid polymers called
polypeptides
How are amino acids formed
Through condensation reactions
Bonds between amino acids called
peptide bonds
Primary structure of proteins
The unique sequence of amino acids which form the polypeptide with varying R-groups
What does tRNA do
Carries the correct amino acid to the next position of the growing chain
What step of DNA replication is where amino acids are joined together?
Translation -> forms the primary structure
Transcription produces the mRNA which contains the code for translation into the actual amino acid chain
How do bonds specifically form between amino acids?
Between the carboxyl and amino group a C-N peptide bond forms
Alipathic amino acids
Hydrocarbon (akyl) chains and a benzene ring
Explain the destination of proteins after translation has been complete (in terms of the ribosomes they’re synthesized by)
Bound ribosomes (ER)
-could remain in cytosol
-enzymes for glycolysis or structural proteins of cell
-targeted to various cell organelles
Proteins synthesized by free ribosomes
-found in cytosol
-can be transported into the nucleus
-histone proteins or transcription factors
-head to the mitochondria or chloroplasts
-become membrane proteins in these organelles
How does a polypeptide obtain it’s shape?
By the interactions between the R-groups
Secondary structure + the types of secondary structures
The interaction between the protein’s backbone
Alpha helix
-spiral/coil due to their hydrogen bonds
- Carbonyl of carboxyl group one 1 amino acid + amide of amino group of another amino acid 4 positions away
-R groups stick out of helix due to hydrogen bonds
Beta plated sheets
-parallel proteins strands with hydrogen bonds formed between carboxyl and amino groups
Tertiary structure
The interactions between R-groups which allow the protein to bend and fold and obtain it’s 3D shape
bonds: H-bonds, london, ionic, disulfide, hydrophobic interactions, covalent
-forms properly folded proteins
-helps support and hold the shape
What are the two assistants that help with protein folding, describe them
Molecular chaprones:
proteins that bind to the hydrophobic regions of the polypeptide and prevent incorrect folding
Chaperonins: molecular complexes which form isolation chambers with a protein inside so it can fold without interference
Quartneary structure
The assmebling of different subunits of tertiary structures to form the fully functional protein
Endomembrane system components
lysosome, ER, golgi, vacuoles, nuclear envelope
for protein and lipid synthesis
How were today’s eukaryotes derived (endomembrane system)
From the invagination of an ancestral prokaryote which contained genetic, heritable material.
Explain what happens when a ribosome becomes bound to the ER (all steps 7 + substeps)
- mRNAs that code for proteins for the endomembrane system have a special signal sequence that once translated, causes the ribosomes to become bound to the ER.
- The protein then enters the lumen for further processing (folding)
- It can then either leave or continue to the final destination by vesicles pinching off the ER
- if it stays then it can undergo glycosylation which is the addition of a carbohydrate chain in a protein
-cell to cell recognition, stability, folding
- The vesicles will fuse with the golgi apparatus and deposit their contents into the golgi lumen
- Further protein modification will occur
-glycosylation can also occur here
Proteins either stay or leave again through vesicles
- proteins go to several different destinations
- cell membrane (porins/receptors/transmembrane proteins)
- secreted out of cell (antibodies, hormones, enzymes)
- other organelles (lysosome, vacuoles)
They are all sorted by a TAG which allows it to be transported through a certain vesicle and can fuse their contents with the phospholipid bilayer of destination
- These vesicles reach their proper location by the cytoskeleton which is a dense network of fibers that maintain/change cell shape
-microtubules stretch through the cell
-cellular roadways
-kinesin nd dynein attach transport vesicle and walk along microtubules using ATP
What is glycosylation
Then addition of a carbohydrate chain onto a protein
-usually occurs on membrane bound proteins
-protein stability, folding, and cell-to-cell recognition
How do vesicles reach their locations?
They are assisted by the cytoskeleton which maintains the structure of the cell by microtubules which vesicle attaches onto kinesin and dyenin and they walk along the microtubules.
What kind of DNA do prokaryotic cells have?
They have cirucular DNA called plasmids or in their nucleoid (majority in here)
Circular DNA
-carries 1 to 2 genes
-replicate independetly of core genome
-transferred from one cell to another
Why do bacteria replicate so fast?
They contain circular DNA which replicate independently of their core genome and are able to move from one cell to another
Chromosome composition
Contains DNA and proteins and RNAs
Difference between prokaryotic and eukaryotic chromsomes
Prokaryotic: nucleoid + circular chromosomes
-> these are supercoiled into loops
Eukaryotic: large linear chromosomes
Supercoiling
A way of compacting DNA while perserving the double helix structure
What would be the purpose of circular DNA in prokaryotes?
They could contain chromosomal DNA with genes needed for survival
How did Griffith/neufled disvoer the hereditary material
They discovered that a hereditary material that could cause a cell to change
Took S-strain
R-strain
heated killed S-strain + R strain = dead
Heated s strain = alive
He realized that the R-strain had undergone transformation meaning that it had uptaken some genetic hereditary material from outside of its cell.
Avery, McLead and Mccarty
They discovered that the DNA molecule was the hereditary material in the cell.
They took enzymes to kill a certain macromolecule leaving the rest alive and observed which one was the hereditary material
Subunits of DNA
nucleotides
What is the composition of a nucleotide
phosphate group
5-carbon deoxyribose sugar
nitrogenous base
Pyrimidines
Cytosine and thymine
Purines
Guanine and adenine
Explain the bonding of nucleotides !!!!!!!!!!!!!!
A phosphodiester bond forms between 2 nucleotides
The 5’ carbon forms a bond with the 3’ carbon on the next deoxyribose
Backbone is in 5’ to 3’ polarity !!!
- added to the 3’ end
Nitrogenous base sticks out of the backbone
What end are nucleotides added
3’ end
Goes in 5’ to 3’ direction
Rosalind Franklin discoveries(4)
She used X-ray cystallography to bombard samples of DNA and then it defracted a shape
-she discovered the helical nature
-discovered the sugar phosphate backbone faced out
-x-shape suggesting a clockwise model
-2 H bonds between AT and 3 between GC